1. Field of the Invention
The present invention is in the field of recombinant DNA technology, protein expression, and vaccines. The present invention relates, in particular, to a method of expressing the outer membrane protein P2 from Haemophilus influenzae type b (Hib-P2). The invention also relates to a method of purification and refolding of the recombinant protein.
2. Background Information
Haemophilus influenzae type b causes bacterial meningitis and other invasive infections in children under the age of 4 years in the United States. The P2 protein from several H. influenzae type b strains has been purified and characterized (Munson et al., J. Clin. Invest. 72:677-684 (1983) and Vachon et al., J. Bacteriol. 162:918-924 (1985)). The structural gene encoding the P2 protein type 1H has been cloned and the DNA sequence determined (Hansen, E. J. et al., Infection and Immunity 56:2709-2716 (October 1988); Hansen, E. J. et al., Infection and Immunity 57:1100-1107 (April 1989); and Munson, Jr., R. and Tolan, Jr., R. W., Infection and Immunity 57:88-94 (January 1989)).
Although recombinant P2 genes have been expressed in H. influenzae Rd (Hansen, E. J. et al., Infection and Immunity 56:2709-2716 (October 1988)) and in E. coli (Munson, Jr., R. and Tolan, Jr., R. W., Infection and Immunity 57:88-94 (January 1989)), the level of expression present in E. coli was low, possibly due to the toxicity of the P2 protein in E. coli as suggested by Munson (Munson, Jr., R. and Tolan, Jr., R. W., Infection and Immunity 57:88-94 (January 1989)) and Hansen (Hansen, E. J. et al., Infection and Immunity 56:2709-2716 (October 1988)). The present invention provides a method of expressing Hib-P2 in E. coli wherein the Hib-P2 protein comprises more than 2% of the total protein expressed in E. coli.